An important parameter of a propagating electromagnetic wave is its polarization, which is the orientation of the electromagnetic wave's electric field in the plane perpendicular to the direction of propagation. Polarization is commonly used to increase data capacity of a given band of frequencies. Thus, techniques for controlling and manipulating polarization are important to radio communications.
Open-ended waveguides and slots cut through waveguide walls are often used to radiate radio waves. The open end (or slots) of the waveguide typically has a rectangular shape with dimensions of about one-half wavelength of the propagating electromagnetic wave in the long dimension and about one-fourth wavelength or less in the short dimension. This results in linear polarized radiation oriented along the short dimension.
In order to rotate polarization in a waveguide transmission line, the waveguide is typically twisted gradually, or stepped, about the axis of propagation. As a typical waveguide has a rectangular profile with a larger width than height, the twisting results in a new aspect ratio. For example, a ninety degree twist in a waveguide that starts with a width-to-height aspect ratio of a/b, and ends with a width-to-height aspect ratio of b/a. This can preclude the use of a waveguide in certain applications where the aspect ratio is critical, such as in certain volume constrained applications.
Thus, a need exists in the art for systems and methods that overcome one or more of the above-described limitations.